1. Field of the Invention
This invention relates to sizing of substrates such as cellulose.
2. Description of the Art Practices
The production of various substrates such as cellulose into paper requires large volumes of water. Accordingly, many of the substrates, even when dried, are still substantially hydrophilic in character and thus may tend to tear or decompose rapidly in the presence of water.
The problem of decomposition of a substrate such as paper in the presence of water is controlled by sizing in the substrate. A size is a material which is itself hydrophobic in nature and which when applied to the substrate causes the substrate to lose its hydrophilic character thereby repelling water. A material which is extremely lightly sized would be toilet paper whereas a corrugated or cardboard box is ordinarily highly sized. Therefore, the amount of size delivered within the present invention is determined by the end-use of the substrate.
Various substrates which may be sized are described in U.S. Pat. No. 4,029,544 issued June 14, 1977 to Jarowenko et al. The substrates suggested by Jarowenko et al include materials such as cellulose (paper); synthetic materials such as polyamides, polyesters and polyacrylic resins, and mineral fibers such as asbestos or glass and mixtures thereof. All of the foregoing materials may be treated with a size to strengthen the substrate. Substrates which are not particularly hydrophilic may be strengthened or the migration of water through the substrate lessened by utilizing a size on a substrate.
It is suggested that the reader review U.S. Pat. No. 3,459,632 issued Aug. 5, 1969 to Caldwell et al for polymers containing both anionic and cationic groups which are useful as sizing aids. A disclosure of cationic polymers useful in sizing include those disclosed in U.S. Pat. No. 4,268,352 issued May 19, 1981 to Cosper et al. Further disclosures of quaternary ammonium starch ethers containing anionic covalent phosphorus moieties are located in Moser et al issued Feb. 9, 1971 as U.S. Pat. No. 3,562,103.
A disclosure of stable, pumpable, solvent-free colloidal polyampholite latices are described in U.S. Pat. No. 4,305,860 issued Dec. 15, 1981 to Iovine et al. The amphoteric starches of Iovine et al are useful herein when in their cationic form. U.S. Pat. No. 3,854,970 issued Dec. 17, 1974 to Aitken describes cationic starches which may be utilized in the sizing of paper. Sweeney in U.S. Pat. No. 4,431,826 issued Feb. 14, 1984 describes various quaternary (cationic) polymers for use in paper sizing.
Ketene dimer emulsions useful as internal paper sizes are described in U.S. Pat. No. 3,524,796 issued Aug. 18, 1970 to Yui. Yui further discloses the use of cationic potato starch in the application of size to a paper substrate.
The use of anhydrides as sizes in paper making are discussed in an article entitled The Role of Alkenyl Succinic Anhydride In Alkaline Paper-Making. The foregoing paper was presented by Maher at the 1982 Paper-Makers Conference and was reprinted in the 1982 TAPPI Procedings at pages 45-50. A further disclosure of alkaline sizing processes is reported in High Ash Paper-Making With Alkaline Sizing presented by Rolland F. Sirois at the 1982 Paper-Making Conference. The foregoing article was reported in the 1982 TAPPI Procedings at pages 63-68.
Various types of anhydride paper sizes are known such as those disclosed in U.S. Re. Pat. No. 29,960 issued Apr. 10, 1979 to Mazzarella et al. Further disclosures of anhydride paper sizes are described in U.S. Pat. No. 4,514,229 issued Apr. 30, 1985 to Sato et al.
Several sizing agents are described in U.S. Pat. No. 4,381,367 issued Apr. 26, 1983 to von Bonin et al. Copolymers of maleic anhydride dicyclopentadiene and vinylcyclohexene as anionic paper sizing materials are described in U.S. Pat. No. 4,316,977 issued Feb. 23, 1982 to Gude et al. Sizing agents based on maleic, phthalic or succinic anhydride or combinations thereof are described in U.S. Pat. No. 4,212,704 issued July 15, 1980 to Durand et al.
U.S. Pat. No. 4,152,312 issued May 1, 1979 to Sackmann et al describes anionic sizes for paper based on esters or semi-esters of diisobutylene/maleic acid anhydride copolymers in the form of their alkali, amine or ammonium salts. Bateman et al in U.S. Pat. No. 4,127,418 issued Nov. 28, 1978 describes various sizing agents based on monoesters of benzene carboxylic acid anhydride. Anhydrides of vinylidene olefin are disclosed in U.S. Pat. No. 3,968,005 issued July 6, 1976 to Wurzburg.
It has not yet been appreciated that the level of sizing agent, particularly those based on anhydrides, may be substantially reduced without adversely affecting the properties of a substrate through the use of the compositions of the present invention. Moreover, the effectiveness of the size may be substantially increased through the processing suggested in the present invention. The delivery and retention of the size to the substrate is enhanced by the present invention.
To the extent that the references reported herein are applicable to the present invention, they are herein incorporated by reference. Percentages and ratios are by weight, temperatures are in degrees Celsius, and pressures are in KPascals unless otherwise indicated.